Re: Differences between SG1495N, MC1495L, and MC1495P?

>Hello,
>
> I recently had to replace an SG1495N in the Y output section of a
>Tempest boardset. At first, I used a MC1495L, and the y output was too
large,
>even with the y-size pot turned all the way down. I then tried a MC1495P,
and
>the y output was great.
> Can anyone please explian the differences between the MC1495L, MC1495P,
>and SG1495N? Perhaps there are datasheets on line for these?

I work with these chips frequently but don't have the datasheets handy at
the moment (they're all at my workplace). Machine-tool industrial motor
drive controllers use them in analog feedback circuits.

The 1495 is an analog switch. When turned off, it prevents a signal from
passing through it. When turned on, it lets the signal pass. The problem
is, when turned on, the chip still presents a fair amount of resistance
(load) to the signal. This amount of resistance is notoriously variable;
not just from manufacturer to manufacturer, but also from one particular
type of chip to the next from the same company.

When I do static tests on these chips, sometimes I read 38 ohms or so.
Sometimes its 50 ohms. Sometimes it's 68 or 70 ohms.

Atari used these chips to invert (or NOT invert) the polarity of an X/Y
video signal. When turned on by a TTL signal, the analog switch would turn
on and would therefore re-route the video signal into an op-amp-based
inversion circuit. This was done to "flip" the picture on cocktail games.
I recently ran into a _Tempest_ board that had a problem with one of these
analog switch chips; it always kept the picture flipped from left to right,
so that instead of "GAME OVER," it always said "REVO EMAG".

Sekips Diova,

Matt J. McCullar
Arlington, TX

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Wed Dec 27 11:30:00 2000